2-D bar code scanner/decoder having a redundancy canceller

• US 5,477,042 A
• Filed: 06/01/1993
• Issued: 12/19/1995
• Est. Priority Date: 06/01/1993
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Metamedia Corporation
• Inventors: Wang, Ynjiun P.
• Primary Examiner(s): FONT, FRANK G
• Assistant Examiner(s): FONT, FRANK G
• Application Number:
  US08/069,581
• Time in Patent Office: 931 Days
• Field of Search: 235/462, 235/467, 235/472
• US Class Current: 235/462.1
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence

Abstract

Hand-held devices are provided for both scanning and decoding coded images such as two-dimensional bar codes. A linear scanning array of image sensing elements in the scanner/decoder provides image data with pixel-to-pixel synchronism, but lacking scan-to-scan synchronism as the scanning array is moved transversely across the bar code image. No tracking ball or roller is included to provide data enabling scan-to-scan synchronism. Redundant scan cancellation is employed to delete redundant image data from the stored image, with the adequate representation of coded information taking precedence over storage of a high resolution image. The stored image is sampled to correlate bar code edge pattern elements in order to identify the bounds and orientation of scanned bar code images. The redundancy-reduced stored bar code image is decoded within the hand-held unit, with use of data on bar code bounds and orientation, to provide decoded information for further use. Scanner/decoder devices and methods, and data redundancy reduction methods are described.

Claims

1. A hand-holdable bar code scanner/decoder, for decoding a two-dimensional bar code image including a plurality of rows of coded information with a start pattern and row coding, comprising:

a linear array of image sensing means extending in a first direction for providing undecoded image data representing a first scan across an image area, including said bar code image, transversely to said start pattern and for providing similar undecoded image data representing subsequent such scans as said linear array is moved with arbitrary speed and arbitrary direction transversely to said rows of coded information;

a redundancy canceller, coupled to said linear array, for deleting redundant undecoded image data on a basis utilizing comparison of said image data representing said first scan with said image data representing a subsequent scan, to provide redundancy reduced image data representative of said bar code image;

a storage device, coupled to said redundancy canceller, for storing redundancy reduced image data;

decoder means, coupled to said storage device and operating without access to tracking data representative of either said arbitrary speed or of said arbitrary direction, for decoding said two-dimensional bar code image by use of said redundancy reduced image data, and said start pattern and row coding as appropriate, to derive decoded information; and

an output port, coupled to said decoder means, for coupling said decoded information out of said scanner/decoder.

2. A bar code scanner/decoder as in claim 1, wherein said linear array is a plurality of charge-coupled devices spaced in said first direction.

3. A bar code scanner/decoder as in claim 1, wherein said redundancy canceller includes a scan buffer able to store said image data in the form of pixel data representing said first scan for comparison with similar pixel data representing said subsequent scan, and said predetermined basis comprises deleting pixel data representing an entire scan when all correspondingly positioned pixels in said first and subsequent scans have the same values based upon said comparison.

4. A bar code scanner/decoder as in claim 1, wherein said first scan and said subsequent scan are successive scans.

5. A bar code scanner/decoder as in claim 1, wherein said two-dimensional bar code also includes a stop pattern and said decoder means uses both said start pattern and said stop pattern as appropriate to derive said decoded information.

6. A bar code scanner/decoder as in claim 1, wherein said image data representing subsequent scans is provided as said linear array is moved transversely to said rows of coded information with one or more of varying arbitrary speed and varying arbitrary directions.

7. A bar code scanner/decoder as in claim 1, additionally comprising:

image buffer means, in the form of said storage device, for storing said redundancy reduced image data to provide a stored image representative of said bar code image;

locator means, coupled to said image buffer means, for using said stored image to develop identification of the bounds and orientation of said bar code image within said image area;

and wherein said decoder means additionally uses said identification of the bounds and orientation of said bar code image in deriving said decoded information from said stored image.

8. A bar code scanner/decoder as in claim 1, wherein said bar code also includes a stop pattern and said scanner/decoder additionally comprises:

image buffer means, in the form of said storage device, for storing said redundancy reduced image data to provide a stored image representative of said bar code image;

sampling means, coupled to said image buffer means, for sampling said stored image along equally spaced parallel lines in a plurality of directions across said bar code image to provide parallel samplings;

correlating means, coupled to said sampling means, for using said parallel samplings to provide correlating data identifying start and stop patterns as representative of a common bar code image when two start patterns, or two stop patterns, are present in successive parallel samplings extending in the same direction and also when start and stop patterns are present in the same parallel sampling with not more than a predetermined separation between said start and stop patterns; and

coordinate identifying means, coupled to said correlating means, for using said correlating data identifying start and stop patterns representative of a common bar code to develop identification of the bounds of said bar code image within said image area;

and wherein said decoder means additionally uses said identification of said bounds of said bar code image in decoding said coded information from said stored image.

9. A scanner/decoder, for decoding a coded image including a plurality of parallel rows of coded information of finite row width and extending in a coding direction normal to said row width, comprising:

a linear array of image sensing means extending in a first direction for providing undecoded image data representing a first scan across an image area, including said coded image, transverse to said row width and for providing similar undecoded image data representing subsequent such scans as said image sensing means is moved with arbitrary speed and arbitrary direction transversely to said coding direction;

a redundancy canceller, coupled to said image sensing means, for deleting redundant undecoded image data on a basis utilizing comparison of said image data representing said first scan and said image data representing a subsequent scan, to provide redundancy reduced image data representative of said coded image;

an image storage device, coupled to said redundancy canceller, for storing said redundancy reduced image data to provide a stored image representative of said bar code image;

decoder means, coupled to said image storage device and operating without access to tracking data representative of said arbitrary speed or arbitrary direction, for decoding said coded image to derive decoded information; and

an output port, coupled to said decoder means, for coupling said decoded information out of said scanner/decoder.

10. A scanner/decoder as in claim 9, additionally comprising:

locator means, coupled to said image storage device, for using said stored image to develop identification of the bounds of said coded image within said image area;

and wherein said decoder means uses said identification of the bounds of said coded image in deriving said decoded information.

11. A scanner/decoder as in claim 9, wherein said redundancy canceller means deletes image data representing an entire scan when redundancy between said first and subsequent scans is indicated based upon said comparison on said basis.

12. A method, for using image data which is synchronized for only one dimension to decode a two-dimensional bar code image including a plurality of rows of coded information of finite row width and extending in a coding direction normal to said row width, comprising the steps of:

(a) scanning an image area including said bar code image by placing a linear array of image sensing elements across said bar code image transversely to said row width to provide undecoded image data representing a first scan across said bar code image;

(b) moving said linear array with arbitrary speed and arbitrary direction transversely to said coding direction to provide undecoded image data representing subsequent scans across said bar code image;

(c) comparing said step (a) image data representing said first scan with said step (b) image data representing a subsequent scan;

(d) cancelling redundant undecoded image data by deletion of image data from one of said first and subsequent scans, if said image data is determined to be redundant, to develop redundancy reduced undecoded image data representative of said bar code image;

(e) storing said redundancy reduced undecoded image data representative of said bar code image;

(f) decoding said bar code image by use of said stored redundancy reduced undecoded image data.

13. A method as in claim 12, including between steps (d) and (e) the additional step of:

(x) analyzing said step (d) redundancy reduced image data to provide identification of the bounds and orientation of said bar code image;

and wherein said identification of said bounds and orientation is utilized in said step (f) decoding.

14. A method as in claim 13, wherein said two-dimensional bar code also includes start and stop patterns extending in the direction of said row width and each row of coded information includes row coding data, and wherein said start and stop patterns are utilized in step (x) in identification of said bounds and orientation of said bar code image and said row coding data is utilized in step (f) in decoding said bar code image.

15. A method as in claim 12, wherein said image data is image pixel data and wherein in step (c) said image data is compared on a pixel-by-pixel basis to determine equality of pixel values and in step (d) all image data is deleted from one of said first and subsequent scans as redundant if all correspondingly positioned pixels in said two scans have equal values when compared on said basis.

16. A method for cancelling redundant image data resulting from scanning of a two-dimensional coded image including a plurality of rows of coded information, each row having a finite width dimension, comprising the steps of:

(a) providing undecoded image data representing a first scan across said coded image transversely to said width dimension;

(b) providing undecoded image data representing a plurality of subsequent such scans laterally spaced in said width dimension;

(c) comparing said image data representing said first scan to said image data representing a subsequent scan;

(d) cancelling redundant undecoded image data by deletion of image data from one of said first and subsequent scans if determined to be redundant when compared in step (c);

(e) repeating steps (c) and (d) based upon comparison of image data representing other scans of said plurality of subsequent scans, to provide selected undecoded image data comprising said image data after deletion of redundant image data; and

(f) making available from step (e) selected undecoded data, representative of the coded content of said coded image, for further processing.

17. A method as in claim 16, wherein step (c) said includes comparison of each pixel of the image data of two scans on a pixel-by-pixel basis, and wherein redundant image data is cancelled in step (c) by deletion of image data comprising one full scan if the image data of two scans have corresponding values on a pixel-by-pixel basis.

18. A method as in claim 17, wherein image data provided for comparison in step (c) is represented by pixel data having one of only two values representative of black or white bar code image portions.

19. A method as in claim 16, wherein step (c) is implemented by comparing image data of two successive scans.

20. A method as in claim 16, wherein said image data provided in step (a) represents scans across a coded image which is a two-dimensional bar code.

21. A hand-holdable bar code scanner/decoder, for decoding a two-dimensional bar code image including a plurality of rows of coded information with a start pattern and row coding, comprising:

a linear array of image sensing means extending in a first direction for providing undecoded image data representing a first scan across an image area, including said bar code image, transversely to said start pattern and for providing similar undecoded image data representing subsequent such scans as said linear array is moved with arbitrary speed and arbitrary direction transversely to said rows of coded information;

a redundancy canceller, coupled to said linear array and arranged to provide redundancy reduced undecoded image data representative of said bar code image and to cancel image data that is redundant to said redundancy reduced undecoded image data;

a storage device, coupled to said redundancy canceller, for storing redundancy reduced image data;

decoder means, coupled to said storage device and operating without access to tracking data representative of either said arbitrary speed or of said arbitrary direction, for decoding said bar code image; and

an output port, coupled to said decoder means, for coupling said decoded information out of said scanner/decoder.

22. A bar code scanner/decoder as in claim 21, wherein said redundancy canceller provides redundancy reduced undecoded image data which may include scans representative of one or more partial rows of coded information as a result of said movement of the linear array with said arbitrary direction, and wherein image data is not decoded prior to coupling of redundancy reduced undecoded image data to said decoder means.

23. A bar code scanner/decoder as in claim 21, wherein said first scan and said subsequent scan are successive scans.

24. A bar code scanner/decoder as in claim 21, additionally comprising an image storage device, coupled to said redundancy canceller, for storing said redundancy reduced undecoded image data to provide a stored image representative of said bar code image for decoding by said decoder means.